Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: jduncan on October 25, 2010, 09:36:58 am
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The numbers are coming and it looks suit:
http://www.dxomark.com/index.php/en/Camera-Sensor/Compare-sensors/(appareil1)/668|0/(appareil2)/485|0/(appareil3)/579|0/(onglet)/0/(brand)/Pentax/(brand2)/Nikon/(brand3)/Phase%20One
It is important to notice that the Pentax do not become the more expensive 15mpixel camera in other to achieve good dynamic range and noise levels above iso 800.
Also note that the tonal range, dynamic range color sens and signal no noise ratio are better until or around where sensor+ kicks in.
The D3x is better in the same range, but it is a 24mpixels 35mm SLR.
Let see how the line evolves
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Wow, very impressive!
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Yet the 645D will be perceived by most users as having one stop less DR than the Phaseone P40+...
http://www.dxomark.com/index.php/en/Camera-Sensor/Compare-sensors/%28appareil1%29/668|0/%28appareil2%29/592|0/%28onglet%29/0/%28brand%29/Pentax/%28brand2%29/Phase%20One
...for the sole reason that they stick to the ISO definition of sensor sensitivity while Phaseone under-exposes their images one stop to give the illusion of magical highlight recovery. :)
Cheers,
Bernard
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Ah those forked tongues... snake oil?
Rob C
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The other stuff that call my attention since the introduction is the price and the fact that it will do 1.1 fps.
Does anybody have info about the sensor? Is it a next generation from kodak?
It looks to me that it is of the same size than the H4D-40 one.
Resolution is little higher.
Pentax has the advantage to be able to use custom asics for the 645. It can finance them because of the DSLRs.
Is that what buys them the higher frame rate?
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It looks to me that it is of the same size than the H4D-40 one.
It is said to be the very same sensor.
Regards,
Bernard
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Hi,
It also said that the sensor in the D3X is very similar to the Sony Alpha 900, but many authors, including yourself, found that the Nikon D3X is clearly superior in most aspects.
What I mean is that it's not just the sensor but also the electronics and the ASICs handling the data.
Best regards
Erik
It is said to be the very same sensor.
Regards,
Bernard
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they stick to the ISO definition of sensor sensitivity
Yes, I noticed that.
And if you look at their SNR, they are higher than the P65+, too! If you downsample to an 8MP file, of course, the P65+'s 60MP do provide an advantage...
Impressive stuff, Pentax! I know they're "just getting going" in the digital MF space, but with this performance and price point, I'd love to see a 60+ MP offering from them...
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promising and definitely worth investigating, $11+k for a kit versus $20K resp. $21K for the corresponding Hasselblad and Phase One 40MP offerings,
that is a huge price difference, even if the 2 other systems proved out to be slightly better...
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promising and definitely worth investigating, $11+k for a kit versus $20K resp. $21K for the corresponding Hasselblad and Phase One 40MP offerings,
that is a huge price difference, even if the 2 other systems proved out to be slightly better...
Uh the Hasselblad H4D40 goes for 18k without lens. This system is much more than just a 40MP sensor comparison.
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It is said to be the very same sensor.
Regards,
Bernard
Does any body knows why the H4D-40 is not in the DxO drop down? it has been a long time.
promising and definitely worth investigating, $11+k for a kit versus $20K resp. $21K for the corresponding Hasselblad and Phase One 40MP offerings,
that is a huge price difference, even if the 2 other systems proved out to be slightly better...
Yes, as long as the person don't need (or wants) to use a technical camera. The other question is the AF lens line.
The ability to travel and have support is important too, even more with a new system. But as you said is really worthy of a good look.
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Uh the Hasselblad H4D40 goes for 18k without lens. This system is much more than just a 40MP sensor comparison.
Not sure what your point is. I never claimed the opposite. I just pointed out that given the price differences of $9-11K between standard kits (I know the body costs less) to a lot of people the Hasselblad and the Phase One 40MP offerings would need to be significantly better to justify the purchase.
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...for the sole reason that they stick to the ISO definition of sensor sensitivity while Phaseone under-exposes their images one stop to give the illusion of magical highlight recovery. :)
Ummm.. what is this info based on? Because its simply not true. The Phase One uses a dalsa sensor, and the Pentax a Kodak ccd with micro lenses. The micro lenses are the reason for the 100 base ISO, vs 50 on the Phase which does not have micro lenses.
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Ummm.. what is this info based on? Because its simply not true. The Phase One uses a dalsa sensor, and the Pentax a Kodak ccd with micro lenses. The micro lenses are the reason for the 100 base ISO, vs 50 on the Phase which does not have micro lenses.
Please check the graph I had linked to.
The ISO 200 of the phase one P40+ is measured to correspond to a real sensitivity of ISO 100, this has nothing to do with the base sensitivity of the sensor.
The only think I did is to translate in words what that graph shows.
Regards,
Bernard
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A waste of everyone's time.
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A waste of everyone's time.
Yours, maybe. Not mine. I am glad to see these measurements. In particular, the "Sports" parameter (Low-light ISO) falls between the PhaseOne P40+ and P65+ scores, but it doesn't have to drop to 1/4 the megapixel resolution to do so. Thanks to microlenses and low readnoise (by MF CCD standards, not by DSLR CMOS standards), this is a MF camera which can do high ISO at high resolution. The H4D-40 should be the same.
There's one glaring omission in all the DxOmark tests, however: they really should test for long exposure image quality (dark noise) as well.
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Please check the graph I had linked to.
The ISO 200 of the phase one P40+ is measured to correspond to a real sensitivity of ISO 100, this has nothing to do with the base sensitivity of the sensor.
The only think I did is to translate in words what that graph shows.
Regards,
Bernard
Ahh, I see where you are coming from! sorry about that. The problem is that I think you are inferring something from the DXO results that may not be the case (that it is artificially low for highlight recovery). I've been trying to find a description for how DXO is measuring ISO but haven't found one yet and I suspect their results are as much an issue of their test methods as they are the properties of the camera. For instance look at their measurements for the H3dII39 and 50 and which indicate that all ISO settings measured only 46 or 47.
Let me preface the next section saying that I've been shooting medium format for some time and have always preferred it to 35mm. Maybe its psychological but i think it helps me create better images by the very fact it forces me to slow down a bit. and of course once you know how to get the best quality it is addicting!
All this said, DXO numbers give us some useful insight, but still is no substitute for actual use. I got some hands on time with the 645D a month and half ago (albeit brief). The camera has some good points and hopefully a good future, but I just don't think its "there yet."
Pros:
-Great auto focus, smooth quiet, responsive. Hard to tell if it was necessarily faster then phase or hasselblad, but it was more polished.
-Great LCD screen.
-Light, felt good in the hands.
-ISO 800 looked very usable
Cons:
-Normal ISO range was 200-800 and 200 is treated as base and default ISO. (apparently you can do 100 and 1600 with some trickery, perhaps they are treating them as fake ISO like 50 on some Canon?). If ISO 200 looked like 50 or 100 on other backs this would be a Pro, but it looked like 200, I.E. some noise present in the shadows and not as sharp as it could be.
-Buttons everywhere. Some people may find this a positive, personally I didn't like it, but to each their own.
-Viewfinder puts your face right up against the screen and is also not that bright.
-Most importantly Image quality in the DNG files looked more like a 40mp 35mm DSLR rather than the quality I am used to seeing from Phase and Leaf backs. This may be due to ISO 200 being the base, the fact that the camera uses only 14bit AD conversion, or that software support is still quite limited. Either way it was a let down.
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There's one glaring omission in all the DxOmark tests, however: they really should test for long exposure image quality (dark noise) as well.
totaly agree with you: Good tripod base iso long exposure is the way to go for a lot of subjects.
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Ahh, I see where you are coming from! sorry about that. The problem is that I think you are inferring something from the DXO results that may not be the case (that it is artificially low for highlight recovery). I've been trying to find a description for how DXO is measuring ISO but haven't found one yet and I suspect their results are as much an issue of their test methods as they are the properties of the camera. For instance look at their measurements for the H3dII39 and 50 and which indicate that all ISO settings measured only 46 or 47.
Whether it was a conscious decision is not that relevant IMHO. It looks too perfect a deviation to be incidental though as it is exactly one stop at all ISOs.
I have not found a detailed definition of their ISO measurement either except a description that they are fully compliant with ISO standards, which would mean that the ISO is measured the same way it was in the film days.
One thing is sure though, if you meter the same way with a 645D and a P40+, you will end up with an image that is one stop under-exposed with the P40+, even if the in-back histogram or P1 Pro histogram doesn't show this, and this will provide one stop of highlight recovery, giving the impression of a superior DR.
Cheers,
Bernard
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For clarity, DxO Mark references ISO Standard 12232 for ISO and uses the saturation method defined therein. It's also worth noting that ISO measurements are done without a lens mounted to ensure what is being measured is in fact sensor sensitivity, and is not biased by the transmission characteristics of particular optics.
I've been trying to find a description for how DXO is measuring ISO but haven't found one yet
http://www.dxomark.com/index.php/eng/Learn-more/Understanding-DxOMark-Database/Measurements/ISO-sensitivity
And just in case anyone thought Bernard was making this stuff up (from the above link):
"As tests show, the ISO settings reported by camera manufacturers can differ significantly from measured ISO in RAW. This difference stems from design choices, in particular the choice to keep some “headroom” to avoid saturation in the higher exposures to make it possible to recover from blown highlights."
I suspect their results are as much an issue of their test methods as they are the properties of the camera. For instance look at their measurements for the H3dII39 and 50 and which indicate that all ISO settings measured only 46 or 47.
For the sake of completeness, it is worth noting that ISO standard #12232 is not without its critics:
http://doug.kerr.home.att.net/pumpkin/index.htm#ISO-DR (link seems to be down--I'll try to find another)
but despite Mr. Kerr's thoughtful analysis, I don't think it is reasonable to make the claim that DxO's methodology is arbitrary.
To address your example, this is a good example where a lack of understanding led to casting suspicion on the data, instead of, perhaps, asking for clarification. The answer is actually quite interesting: the value recorded for all ISO settings in those Hasselblads is the same is because this camera is not providing hardware based signal gain. DxO's information is telling you that the ISO settings you select on the camera are applied by software, after the capture is made.
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To address your example, this is a good example where a lack of understanding led to casting suspicion on the data. The answer is actually quite interesting: the value recorded for all ISO settings in those Hasselblads is the same is because this camera is not providing hardware based signal gain. DxO's information is telling you that the ISO settings you select on the camera are applied by software, after the capture is made.
As Bernard might say, this explains why at ISO 800 highlight recovery is so good :)
Edmund
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I have not found a detailed definition of their ISO measurement either except a description that they are fully compliant with ISO standards, which would mean that the ISO is measured the same way it was in the film days.
Not really: remember that ISO just refers to the International Organization for Standardization which publishes many standards, including several related to film and sensors, and the ISO standard for film speed is not the same thing as the so-called ISO setting on a digital camera, though they have something in common.
1. The "ISO scale" on a digital camera should relate to Exposure Index, which measures what combinations of subject illumination, shutter speed, and aperture ratio will give a suitable "middle gray" response from the camera. This really should be called exposure index, but the ambiguous and confusing name "ISO" is entrenched.
2. The ISO (formerly ASA) speed rating of a film is roughly the maximum exposure index that gives results meeting a certain standard of shadow handling and such: it is roughly a maximum safe exposure index, based roughly on how well subjects four stops below middle gray are handled.
By the way, there is yet another ISO standard definition worth mention:
3. There is also an ISO standard for "base speed" or roughly the minimum exposure index giving satisfactory highlight handling; based on having about three stops between mid-tone exposure level and blown highlights. Quite different from ISO film speed.
Loosely, 1. is about specifying units of measurement (like seconds) while 2. and 3. use those units to measure two quite different characteristics of the "light sensitive medium" (the minimum and maximum acceptable exposure times in those units of seconds under certain conditions on illumination and f-stop.)
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The answer is actually quite interesting: the value recorded for all ISO settings in those Hasselblads is the same is because this camera is not providing hardware based signal gain. DxO's information is telling you that the ISO settings you select on the camera are applied by software, after the capture is made.
Excelent explanation.
It was my first guess when I saw the data. Of course is I am a CS by trying, and this cameras are electronic devices, my bread and butter.
For some photographers its more like me in a convention about car engines for me: I know the general stuff, and the physics , but my intuition and training is not in that area. None of that is any help in driving a car by the way.
Maybe DxO should make a more Photographer friendly, easy to find explanation?.
The lack of gain (signal amplification) could be compared to the difference between fast film and pushing slow film.
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<snip> hich would mean that the ISO is measured the same way it was in the film days.
As Bradley & BJL have explained, that's not how digital ISO is measured.
But just imagine if it was measured using the same basis as film was: minimum exposure required to register some threshold density above base fog, would translate to minimum exposure required to register some threshold signal to noise at a pixel (say, 3 sigma, the normal minimum threshold in science). Instead of all cameras having base ISOs within a factor of 2 or 3 of each other, P&S digicams and phone cams with tiny pixels would be something like ISO 50 while the likes of a Nikon D3 would be something like ISO 3200 - and I'm talking about base ISO. This would correlate roughly with Roger Clark's concepts of Unity Gain ISO (considering signal shot noise only) or Low Light Sensitivity Factor (considering readnoise as well).
That would transform the digital camera scene and the public's perspectives of it! Instead of pursuing largely useless metrics like megapixel count, they would judge on a metric that really does tell you something significant about the capabilities of the sensor, and in what shooting situations it can be expected to perform well or poorly.
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The ISO 12232 standard discusses various methods for characterizing the final output values and how they relate to reported values (e.g., ISO 100, REI). It says nothing about how the raw data itself is recorded in relation to the reported values.
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As Bradley & BJL have explained, that's not how digital ISO is measured.
But just imagine if it was measured using the same basis as film was: minimum exposure required to register some threshold density above base fog, would translate to minimum exposure required to register some threshold signal to noise at a pixel (say, 3 sigma, the normal minimum threshold in science). Instead of all cameras having base ISOs within a factor of 2 or 3 of each other, P&S digicams and phone cams with tiny pixels would be something like ISO 50 while the likes of a Nikon D3 would be something like ISO 3200 - and I'm talking about base ISO. This would correlate roughly with Roger Clark's concepts of Unity Gain ISO (considering signal shot noise only) or Low Light Sensitivity Factor (considering readnoise as well).
Wikipedia (http://en.wikipedia.org/wiki/Film_speed#Noise-based_speed) has a pretty good explanation of the ISO standard 12232:2006 that is used to rate digital camera sensitivity. DXO uses the Saturation-based speed, wherein exposure settings based on a standard light meter and an 18-percent reflective surface will result in an image with a grey level of 18%/√2 = 12.7% of saturation. This allows a half stop of headroom for the highlights. If you want highlights to be at saturation (as in exposing fully to the right) you have to add 1/2 stop of exposure as determined by a gray card reading. This hasn't changed from the film era as explained by Thom Hogan (http://www.bythom.com/graycards.htm).
The ISO also has a SOS rating in which 18% saturation of the sensor corresponds to an 8 bit RGB value of 118 in a gamma 2.2 encoded output space. Strictly speaking this rating does not apply to raw data, since the standard specifies a gamma 2.2 space for a rendered file. However, the concept is often applied for raw data (see Bill Claff (http://home.comcast.net/~NikonD70/Investigations/Sensor_Characteristics.htm), who has compiled ratings for various Nikon cameras). The JPEG engine in most digital cameras and most raw converters apply a tone curve so that the value in the rendered file may well not be 118. To determine the sensor saturation, you have to look at the raw linear data with a program that allows this (DCRaw and Iris are two such programs). For example, a gray card (or for that matter a white card) exposed according to the light meter reading with my Nikon D3 gives a 12 bit value in the green channel of 497, which corresponds to 497/4095 or 12.1% saturation, which is in accord with the ISO 12232:2006 saturation standard. However, the JPEG engine with the Standard Picture Control renders this with a pixel value of 150 in sRGB. This represents a hot tone curve and the rendered image appears overexposed. You really have to know your camera and the rendering hardware.
The standard does allow for a noise based speed rating much as you propose, but this is seldom used. With digital, we really want to expose for the highlights (exposure to the right).
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I agree with ondebanks except on one word, "base".
... P&S digicams and phone cams with tiny pixels would be something like ISO 50 while the likes of a Nikon D3 would be something like ISO 3200 - and I'm talking about base ISO.
Not base ISO. That word "base" in ISO spec's refers to the minimum exposure index giving adequate highlight handling, and it rather naturally does not depend much on pixel size. That ISO 3200 for the D3 would be the maximum exposure index for adequate shadow/noise handling, which I propose calling the "film-like ISO speed". In film exposure/processing terms, the base ISO speed is how far you can safely pull; the shadow/noise based speed limit is how far you can safely push.
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For clarity, DxO Mark references ISO Standard 12232 for ISO and uses the saturation method defined therein. It's also worth noting that ISO measurements are done without a lens mounted to ensure what is being measured is in fact sensor sensitivity, and is not biased by the transmission characteristics of particular optics.
http://www.dxomark.com/index.php/eng/Learn-more/Understanding-DxOMark-Database/Measurements/ISO-sensitivity
And just in case anyone thought Bernard was making this stuff up (from the above link):
"As tests show, the ISO settings reported by camera manufacturers can differ significantly from measured ISO in RAW. This difference stems from design choices, in particular the choice to keep some “headroom” to avoid saturation in the higher exposures to make it possible to recover from blown highlights."
For the sake of completeness, it is worth noting that ISO standard #12232 is not without its critics:
http://doug.kerr.home.att.net/pumpkin/index.htm#ISO-DR (link seems to be down--I'll try to find another)
but despite Mr. Kerr's thoughtful analysis, I don't think it is reasonable to make the claim that DxO's methodology is arbitrary.
To address your example, this is a good example where a lack of understanding led to casting suspicion on the data, instead of, perhaps, asking for clarification. The answer is actually quite interesting: the value recorded for all ISO settings in those Hasselblads is the same is because this camera is not providing hardware based signal gain. DxO's information is telling you that the ISO settings you select on the camera are applied by software, after the capture is made.
I appreciate your inclusion of the link I was looking for.. just couldn't find it before some reason. I didn't mean to suggest their methods were arbitrary, but simply that depending on their methodology they might not tell the whole story.
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Thanks for the clarifications & corrections, bjanes & BJL.
The standard does allow for a noise based speed rating much as you propose, but this is seldom used. With digital, we really want to expose for the highlights (exposure to the right).
There are a few domains away from the mainstream of digital imaging, like deep-sky astrophotography, where we don't have this luxury of ETTR, and a noise based rating would be far more useful. I came to this realisation too late in my own learning process, or more accurately I let my MF-loving heart override my S/N-calculating head, when I bought a used MFDB instead of a 5DII. Surely the bigger pixels and larger total light-gathering surface area would let the MFDB hold its own against the 5DII's lower readnoise? Alas, no. I should have heeded the ISO ratings, and done up those S/N spreadsheet calculations sooner! Still, the MFDB is better at just about all the daytime stuff I like to shoot, so it's not a tragedy; but definitely a disappointment.
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Yes, the ISO 12232 standard has different reporting methods (saturation based, noise based, recommended exposure index), which are reflected in the revised EXIF 2.3 spec.
Again, this has nothing to do with shooting raw, though ...